In firing large caliber weapons, a considerable impulse is generated by the detonated cartridge. This impulse is initially imparted to the breech, which is generally locked to the barrel. In this manner the mechanism which locks the breech to the barrel receives the firing load. Conventional locking mechanisms for this purpose include the lug type, which utilizes one or more locking lugs to retain the breech in the locked position. Sliding breech blocks, which simply slide across the chamber opening, are also used. It is important that the firing load be symmetrically transmitted to the weapon receiver. This is because unsymmetrical forces induce bending moments which can warp or break major weapon components.
In order to symmetrically distribute the firing load, the locking mechanism must engage the weapon receiver symmetrically about the longitudinal axis of the weapon bore. Neither of the aforementioned types of locking mechanisms easily lends itself to this concept.
It is also desirable to insure that locking is complete before the weapon is fired. Conventional locking mechanisms do not normally include means to preclude the possibility of firing a weapon when it is in an unlocked or partially locked condition. Completing locking before firing is desirable to prevent damage to the weapon or the weapon operator.